At present, the 3rd Generation Partnership Project (generally known as “3GPP”) is developing an interworking architecture to allow the interconnection of a 3GPP network with a so-called Wireless Local Area Network (generally known as “WLAN” and also as “hot spots”), wherein the WLAN acts as an access network through which an end-user may access the 3GPP network to make use of services in the 3GPP network, or to simply use the 3GPP network for authentication, authorization and accounting purposes. A 3GPP network may include a number of network nodes and interfaces from different known technologies such as the Global System Mobile (GSM) and the GSM Packet Radio System (GPRS), and from the more recent technology Universal Mobile Telecommunications System (UMTS).
The advantage of this interconnection illustrated in FIG. 1 is a win-win relationship between both parties, namely a WLAN operator and a 3GPP network operator, as well as to end-users. The 3GPP network operator may offer to the end-users a high-speed data access provided by WLAN in places where this high-speed connection may be very useful, such as airports and hotels. Thanks to this interconnection, the WLAN hot spot operator may thus attract more end-users, those who are subscribers of a 3GPP network operator and who can more easily access their 3GPP network.
On the other hand, the 3GPP network operator still keeps on the business chain and ensures an appropriate access security by still carrying out tasks delegated by the WLAN hot spot operator. These tasks, for the time being, may be authentication of the user and charging functions.
Advantageously, the authentication in a 3GPP network make possible for end-users to authenticate with the same method as they use in their 3GPP networks, that is, by means of a user subscription identity module card (a SIM card for GSM users, a USIM card for UMTS users, and hereinafter both referred to as “U-SIM”). In this way, the authentication is transparent to end-users since they do not need to learn passwords or new user identifications to be used for the WLAN access network and, on the other hand, the 3GPP network still has an accurate knowledge that the user being authenticated is actually a subscriber of its network. Besides, charging information may be reported from the WLAN hot spot to the 3GPP network, and therefore the end-user may receive a single bill independently of the access network.
An interesting aspect of this interconnection between a WLAN access network and a 3GPP network is the selection of a Public Land Mobile network (PLMN) as a visited 3GPP network when the user is roaming and wishes to access such visited PLMN (VPLMN) through an available WLAN access network. In other words, the basic issue is to let the user know how the user can reach his home PLMN (HPLMN).
Currently, a user roaming in a GSM domain or in a GPRS domain (hereinafter both indistinctly referred to as “GSM/GPRS domain”) is presented with a list of visited networks where the user can attach, this information being retrieved from storage in the user's U-SIM. There is no mechanism with updated information whereby a user can apply different selection criteria for selecting a visited network (VPLMN) and, even less, dynamic selection criteria depending on most recent service agreements between the home network operator and the different visited network operators.
More precisely, when a subscriber of a home network (HPLMN) tries to register in a visited network whilst roaming, a so-called “Location Update” procedure is initiates towards the home network. In particular, the “Location Update” procedure is initiated through a so-called Mobile Switching Centre (MSC), possibly coupled with a Visitor Location Register (VLR) in a selected GSM visited network (VPLMN) towards a Home Location Register (generally known as “HLR”) or a Home Subscriber Server (generally known as “HSS”) in the home network; or through a Serving GPRS Server Node (SGSN) in a selected GPRS visited network (VPLMN) towards said Home Location Register (HLR) or Home Subscriber Server (HSS) in the home network, depending on whether the access network is a GSM or a GPRS access network. If the home network rejects the registration through the selected visited network, the user equipment is informed about such event and the rejected visited network, or an identifier thereof, is stored in a list of so-called “visited networks forbidden for roaming”.
Any visited network included in the list of “visited networks forbidden for roaming” at the user's equipment side will not be even attempted during further registration procedures, namely “Location Update” procedures, by the user's equipment. In this respect, it would be desirable to find a mechanism whereby subscribers of a home network can be aware of the most recent service agreements between the home network and other visited networks and whereby the home network can let the user be aware of preferences for selecting an appropriate visited network depending on different selection criteria.
In a similar manner, it would be desirable to find a mechanism whereby a user roaming in a WLAN domain can select one of a plurality of visited networks (VPLMN) when connecting through a WLAN access network.
Nowadays, a user equipment adapted to operate in a WLAN access network is able to receive available Service Set Identifiers (SSID), which are identifiers of the WLAN access networks “visible” to the user equipment, but this information is not enough for selecting the most appropriate WLAN access network to reach the home network. In this context, “visible” means that the user equipment can discover and communicate with such access network via radio resources.
A current solution presented in 3GPP, and in fora of the Internet Engineering Tasks Forces (IETF), proposes the use of a special realm, “nonreachable.3gppnetwork.org”, to indicate the WLAN network that the user wants to see the list of visited networks (VPLMN) that can be used to reach the user's home network (HPLMN). Upon receiving such special realm, each visible WLAN network sends back to the user a list of those visited networks (VPLMN), which the WLAN network has a direct connection to, in a format specified by “Identity selection hints for Extensible Authentication Protocol (EAP), draft-adrangi-eap-network-discovery-12. Then, and for an automatic mode, the user equipment receives a list of visited networks (VPLMN) with which each WLAN network has a direct connection. The user equipment selects one network from that list with help of two additional lists that reside in the U-SIM: a first additional list including visited networks (VPLMN) preferred by the operator, and a second additional list including visited networks (VPLMN) preferred by the user. The operator preference list is static and cannot be changed in the U-SIM, whereas the user preference list can be changed by the user at any time by operating the user's equipment. The selection of a visited network (VPLMN) from the received list with help of the two additional lists can be performed in automatic or manual mode.
An important drawback of this solution is that the user can only receive a list of visited networks (VPLMN) that the user may visit, in principle, simply because they have a direct connection to the WLAN, but the user does not have any other valuable information. Moreover, a visited network (VPLMN) selected from this list might later on be rejected by the home network (HPLMN) due to different reasons, such as the visited network being barred for roaming, or a temporary disruption of roaming services between both network operators. This implies that after having selected one WLAN access network for accessing to a certain visited network, such visited network might be rejected by the home network, so that the user would have to repeat the process until selecting an acceptable visited network (VPLMN) accessible through the selected WLAN access network, or until selecting an appropriate WLAN access network where an acceptable visited network (VPLMN) is accessible through; and this iterative process would have to be carried out with repeated accesses to the home network for acceptance of each visited network. This drawback is even worse when the user is moving from a WLAN access network coverage area to another.
Moreover, a user usually selects a visited network (VPLMN) and wants to maintain to that visited network as long as it is reachable. This is a drawback currently in GSM/GPRS networks, where the user equipment automatically tries to switch to other visited network (VPLMN), if the signal strength of that visited network is better than the one the user had selected before, and there must be an acceptance from the home network prior to handover to the new visited network.
Therefore, an object of the present invention is the provision of a mechanism whereby a roaming user can select at least one visited network allowed for roaming by the home network operator among a plurality of visited networks (VPLMN) accessible through an access network.
Moreover, the present invention is aimed to provide users with a simple and accurate mechanism for selection of a visited network when the user is roaming and wishes to connect a WLAN access network in the way the WLAN interworking architecture currently operates.
Further, an object of the present invention is the provision to users of more complete information regarding visited networks and access networks as selection criteria for selecting a particular access network for accessing a particular visited network.